US4987020A - Highly oriented thermotropic magnetic recording medium - Google Patents

Highly oriented thermotropic magnetic recording medium Download PDF

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US4987020A
US4987020A US07/418,964 US41896489A US4987020A US 4987020 A US4987020 A US 4987020A US 41896489 A US41896489 A US 41896489A US 4987020 A US4987020 A US 4987020A
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substrate
units
thermotropic
radical
polymer
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US07/418,964
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Claude Bonnebat
Jean-Pierre Quentin
Alain Morin
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Rhodia Chimie SAS
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Rhone Poulenc Chimie SA
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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17—Component parts, details or accessories; Auxiliary operations
    • B29C45/26—Moulds
    • B29C45/263—Moulds with mould wall parts provided with fine grooves or impressions, e.g. for record discs
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/0001—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor characterised by the choice of material
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/73—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer
    • G11B5/739—Magnetic recording media substrates
    • G11B5/73923—Organic polymer substrates
    • G11B5/73927—Polyester substrates, e.g. polyethylene terephthalate
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/73—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer
    • G11B5/739—Magnetic recording media substrates
    • G11B5/73923—Organic polymer substrates
    • G11B5/73937—Substrates having an organic polymer comprising a ring structure
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S428/00—Stock material or miscellaneous articles
    • Y10S428/90—Magnetic feature
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/31504—Composite [nonstructural laminate]
    • Y10T428/31786—Of polyester [e.g., alkyd, etc.]

Definitions

  • the present invention relates to rigid polymeric substrates based on thermotropic polymers well adapted for use as magnetic recording media, and, in particular, to magnetic recording discs produced therefrom.
  • magnetic recording discs include a circular, rigid substrate which is smooth and thin (thickness on the order of 1 to 2 mm), which generally has a coaxial opening in the center thereof, adapted to receive appropriate holding and driving means, and with at least one of its face surfaces comprising a suitable magnetic coating of very low thickness (for example, 0.3 to 0.5 ⁇ m in the case of the magnetic layers based on magnetic pigments or 0.05 to 0.2 ⁇ m in the case of discs provided with a thin metal surface layer).
  • a suitable magnetic coating of very low thickness for example, 0.3 to 0.5 ⁇ m in the case of the magnetic layers based on magnetic pigments or 0.05 to 0.2 ⁇ m in the case of discs provided with a thin metal surface layer.
  • one or more magnetic read-write heads are arranged in a manner known per se and, when the disc is rotated (speed of rotation on the order of 3,600 revolutions/minute), these "hover" at a height on the order of 0.2 to 0.6 ⁇ m above the surface of the disc.
  • Aluminum alloys such as, for example, alloys based on aluminum (96% by weight) and magnesium (4% by weight) of the AA 5086 type meet these various requirements relatively well. They are, however, materials which are costly to machine or to polish. Furthermore, iron-rich oxidizable intermetallic compounds are generally present within these materials, giving rise to the formation of segregated regions, the size of which ranges from 2 to 10 ⁇ m, and which behave differently either over the course of the machining and polishing, or during aging.
  • Glass can also constitute a material which is relatively well adapted as a magnetic coating substrate for a recording disc.
  • the disadvantages which are attributed to glass in the majority of cases are as follows: firstly, glass is brittle (in materials science, brittleness typically connotes the absence of plasticity and abrupt failure upon impacts); furthermore, glass is costly to work and to polish; and, lastly, problems may also arise in respect of the adhesion of the magnetic coating which it is to receive.
  • polyetherimides such as, for example, the material marketed under the trademark Ultem 1000; however, this polymer has a low rigidity reflected in an elasticity modulus of approximately 3,000 MPa, and a high coefficient of thermal expansion in the radial direction, of approximately 56 ⁇ m/m/°C., which makes it incompatible with all of the existing tracking systems for rigid discs comprising an aluminum substrate; and
  • the figure is a schematic view, in elevation, showing the technique for measuring warp angle of the invention molded substrate.
  • a major object of the present invention is the provision of an improved rigid magnetic recording substrate based on a polymer:
  • fillers While the addition of fillers is a known technique for correcting the natural values of plastics with regard to rigidity (when it is too low) and the coefficient of thermal expansion (when it is excessively high), the use of fillers must be avoided in molding rigid plastic substrates, since their presence can play a role which is detrimental to surface quality.
  • thermoplastic materials may be increased by monoaxial or biaxial drawing, but these processes are inapplicable in the case of a rigid circular substrate which must meet certain criteria of flatness and of uniformity of thickness.
  • a known polymeric material is used, the advantages of which have not been fully realized for the production of substrate destined for use in the manufacture of rigid magnetic recording discs.
  • Such polymeric material exhibits particular intrinsic characteristics which are advantageously and unexpectedly combined under the influence of the conversion conditions in order to impart the desirable properties discussed above.
  • the present invention features a smooth, thin, circular, rigid substrate shaped from a particular polymeric material, for a magnetic recording disc, said polymeric material comprising a thermotropic polymer and having a flow temperature ranging from 200° C. to 350° C. and an inherent viscosity of at least 1 dl g -1 .
  • the substrate according to this invention is subjected to a very high molecular orientation by injection molding the thermotropic polymer into a suitable mold cavity equipped with a central injection system for the polymeric material, and wherein the temperature of the walls of said mold ranges from 100° C. to 200° C., the temperature of the injected molten polymer ranges from 280° C. to 350° C., the injection time ranges from 2 to 10 seconds, the injection pressure ranges from 80 to 160 MPa and the holding pressure after injection ranges from 40 to 120 MPa.
  • the final product molded substrate has a relative density of less than 1.8, a modulus of elasticity in the radial direction ranging from 9,000 MPa to 18,000 MPa, a coefficient of thermal expansion in the radial direction ranging from 10 to 20 ⁇ m/m/°C. and a deformation temperature under load of at least 150° C.
  • the final product molded substrate is also characterized by its substantially perfectly smooth surface as measured by a surface roughness of less than 0.05 m and by a planarity such that the angle of buckling (warm angle) is less than 1 ⁇ 10 -5 radian.
  • the molded circular substrates which are produced have the following principal dimensions: external diameter: from 70 mm to 360 mm; thickness: from 1 mm to 2 mm.
  • the formats which usually are of greatest interest, being the most widely employed, are the following: substrates having diameters of 90 mm (31/2inches) to 130 mm (51/2inches), thus enabling the production of discs having a storage capacity ranging from 5 to 16 megabytes; substrates having a diameter of 200 mm (8 inches) for the manufacture of discs used in microcomputers capable of attaining storage capacities from 10 to 50 megabytes with stacks of several stationary discs; substrates having a diameter of 355 mm (14 inches) intended for stationary disc units of very high capacity.
  • thermotropic polymers which are suitable for use according to the present invention comprise wholly aromatic polyesters, alkylaromatic polyesters, wholly aromatic poly(esteramides), alkylaromatic poly(esteramides), aromatic polyazomethines, aromatic carbonate polyesters and mixtures of such polymers.
  • thermotropic polymers are wholly aromatic polyesters, alkylaromatic polyesters, aromatic carbonate polyesters and mixtures of these polymers.
  • the wholly aromatic polyesters are especially preferred.
  • alkylaromatic polyesters which are thermotropic are described, for example, in U. S. Pat. Nos. 3,778,410, 3,804,805, 4,248,995, 4,311,824 and 4,355,133.
  • thermotropic polymers which are advantageously selected according to the present invention are those which have a flow temperature in the range of from 200° C. to 350° C. and which have an inherent viscosity of at least 1 dl g -1 , and more preferably from 1.1 to 4.0 dl g -1 .
  • flow temperature is intended the temperature at which the edges of a test specimen in the shape of a polymer chip or of a cut fiber begin to become rounded. This temperature is determined by visual inspection of the test specimen on a glass slide-cover at a suitable rate of temperature increase, generally on the order of 10° C. to 20° C. per minute, the observation being made with the aid of a microscope fitted with a heated stage known commercially under the trademark Thermopan.
  • R 1 is a methyl or ethyl radical or a chlorine or bromine atom, with the proviso that the units (I) may either be identical or different;
  • (II) represents the structure: ##STR2##
  • (III) represents the structure: ##STR3##
  • (IV) represents the structure: ##STR4##
  • the molar ratio of the recurring units (I) relative to the sum of the recurring units (II)+(III) ranges from 0.95 to 1.05;
  • the quantity of recurring units (II) in the mixture (II)+(III) ranges from 0 to 70 mole % and that of the recurring units (III), relative to the same mixture, ranges from 100 to 30 mole %;
  • the quantity of recurring units (IV), relative to the quantity of the recurring units (I), ranges from 10 to 300 mole %.
  • alkylaromatic thermotropic polyesters which are most especially preferred are those described in U. S. Pat. Nos. 4,248,995 and 4,311,824. These polyesters include recurring units of the formulae:
  • X 1 is a 1,4-phenylene radical monosubstituted by a methyl or ethyl group or a chlorine or bromine atom,
  • X 2 an unsubstituted 1,4-phenylene radical
  • Y is:
  • the molar ratio Z/Y+Z ranges from 20 to 50%.
  • thermotropic carbonate polyesters which are most especially preferred are those described in U. S. Pat. No. 4,284,757. These polyesters include recurring units of the formulae: ##STR7## in which: the radicals R 4 , which are identical, are each a 1,4-phenylene radical monosubstituted by a methyl or ethyl group or a chlorine or bromine atom;
  • radicals R 5 are each an unsubstituted 1,4-phenylene radical
  • the radicals R 6 which may be identical or different, are each 1,4-phenylene, 1,4-cyclohexylene, 4,4'-biphenylene, 2,6-naphthylene, 4,4'-ethylenedioxy-1,1'-diphenylene, 4,4'-butylenedioxy-1,1'-diphenylene or 4,4'-hexylendioxy-1,1'-diphenylene radicals; and
  • the thin, circular, rigid substrates according to the present invention are produced by an injection molding process effected in the anisotropy region of the thermotropic polymer employed. It will be appreciated that the thermotropy is easy to demonstrate when the polymer in melt form is observed in an optical system equipped with two crossed polarizers (90° C.): birefringence and transmission of polarized light through the crossed polarizers occurs in the case of the anisotropic specimens. Demonstration of the anisotropy of the polyesters according to the present invention has been carried out using the TOT thermooptical method described in French Patent No. 2,270,282.
  • anisotropy region is intended the temperature range which begins with the temperature at which the birefringence and the transmission of light through the two crossed polarizers appear, and which is situated above said temperature, a range which has a variable upper limit and in which the molten mass is anisotropic without any risk of polymer decomposition.
  • the anisotropic molten masses which are injection-molded according to the present invention have an anisotropy region extending over at least 30° C.
  • the molded circular substrates which are produced have a low relative density of less than 1.8 and display the combination of the desired properties More precisely, they have a modulus of elasticity in the radial direction ranging from 9,000 MPa to 18,000 MPa and a coefficient of thermal expansion in the radial direction which is less than 30 ⁇ m/m/°C. and which, as indicated above, preferably ranges from 10 to 20 ⁇ m/m/°C.
  • the coefficient of thermal expansion in the transverse direction ( ⁇ t) will generally and preferably exceed 100 ⁇ m/m/°C., such as from 100 to 250 ⁇ m/m/°C.
  • the ratio ⁇ r / ⁇ t which is a measure of the anisotropy in depth is less than about 0.1.
  • the advantages of the molded substrates which are produced are not restricted to these two properties; it should be noted, in particular, that these materials also have a high DTUL, of at least 150° C., and which can attain values up to 240° C. and even higher, and good dimensional stability with low degree of shrinkage on demolding and that, insofar as physicochemical properties are concerned, they are naturally insensitive to solvents and are only slightly moisture-sensitive.
  • the anisotropic melts employed in the injection-molding operations are characterized by very high fluidity when heated, and this makes it possible to produce shaped articles exhibiting an excellent surface profile.
  • the molded substrates produced are perfectly smooth (surface roughness is less than 0.05 ⁇ m) and have perfect planarity and uniformity of their thickness.
  • substantially perfectly planar or “perfect planarity” is defined as an angle of buckling (warp angle) (defined as the ratio H/R, for a circular molded substrate, where H is the vertical distance between a point on the top surface of the substrate, at the periphery of the substrate and a perfectly smooth marble or glass-like reference surface on which the center of the circular substrate is held, and R is the radius of the substrate measured in the same units as H; see FIG. 1) which is less than 1 ⁇ 10 -5 radian.
  • the substrates produced may be subjected to a heat treatment at a high temperature, but below the melting point of the polymer.
  • the substrates produced are subjected to the conventional treatment intended to produce (or to apply a final finish to) the central aperture, and then they are provided with a magnetic coating on at least one of the face surfaces thereof, after a preliminary degreasing of the surface(s) involved.
  • the present invention also features magnetic recording discs resulting from the magnetic coating of the molded substrates which have been described above.
  • this invention also features magnetic recording discs comprising a smooth, thin, circular, rigid substrate made of polymeric material and having a magnetic coating of particulate or thin-layer type deposited onto at least one of the face surfaces thereof, wherein said substrate satisfies those requirements given above.
  • the magnetic coating layer generally contains magnetic particles which may be, for example, iron oxide ( ⁇ -Fe 2 0 3 plus Fe 3 0 4 if desired), doped, if desired, with cobalt, with passivated iron, with iron nitride or with barium hexaferrite, which are dispersed in a suitable solvent or a mixture of solvents and a suitable binder.
  • the magnetic layer may additionally contain a lubricant, as in the traditional Winchester type method.
  • a lubricant as in the traditional Winchester type method.
  • the coated substrate is subjected to a heat treatment in order to crosslink the binder, this treatment being carried out, for example, at about 200° C. when the binder employed is an epoxy resin.
  • other means of crosslinking may be utilized, depending on the nature of the binder: for example, a radiation or electron beam treatment.
  • the magnetic disc produced is subjected to conventional polishing and cleaning operations.
  • the thickness of the deposited layer based on magnetic pigments generally ranges from 0.3 to 5 ⁇ m, depending on the type of application for which the disc is intended. It should be noted that the disc may be coated with a thin lubricating layer before use.
  • An alternative embodiment includes deposition of the magnetic layer by means of an electrolytic method, provided the substrate has first been metallized.
  • the final product magnetic discs exhibit the combination of desirable properties referred to above in respect of the substrate, especially insofar as the surface quality (roughness, flatness), rigidity (elasticity modulus), dimensional stability (thermal expansion coefficient) and heat resistance (DTUL) are concerned.
  • thermotropic polymer 1. Description of the thermotropic polymer employed
  • a wholly aromatic polyester was prepared, of the type described in European Patent Application No. 86/420,013.4, published under No. 0,191,705.
  • the polymer produced was greyish and fibrous in appearance. It had an inherent viscosity of 1.4 dl g -1 . Its flow temperature was 290° C. The anisotropy region ranged from 290° C. to above 350° C.
  • the polymer was processed on a Battenfeld BSKM 100/70 S DS 2,000 injection molding machine.
  • the circular mold employed, having polished face surfaces, had the following characteristics: diameter: 95 mm ⁇ 0.025 mm; thickness: 2 mm ⁇ 0.025 mm; central injection via a 4-mm diameter nozzle.
  • the molding conditions were as follows:
  • the warp angle is measured (see FIG. 1) by securing the substrate 10 on top of a perfectly smooth reference plane 20 (having a marble-like surface).
  • the distance H between the plate top 22 and substrate top surface 12 at the periphery thereof is obtained by a differential measurement using a transducer 30 with an inductive gauge tip 32 (a Millitron 1202D available from Feinpruf Mahr was used), taking the thickness of the substrate into consideration.
  • the warp angle is taken as the average of 10 measurements made on each of 3 different substrates, the 10 measurements being made at 10 equidistant points on the periphery, i.e. at a spacing of 36°.
  • the moduli and the strength were measured at 23° C. according to French Standard NF T 51034 on dumbbell-shaped test specimens 4 mm in width and 2 mm thick, conditioned at an RH of 50%:
  • the dimensional stability of the substrate was evaluated by means of measurements of the coefficient of linear thermal expansion on parallelepipedal test specimens 5 ⁇ 5 ⁇ 2 mm in size, taken radially ( ⁇ r) and transversely ( ⁇ t ) according to ASTM Standard D 696-70 in a temperature range from -30° C. to +30° C. and under dry nitrogen:
  • the deformation temperature under load was measured according to French Standard NF T 51005; its value was 250° C. (under 1.82 MPa).
  • Crystallinity the structure was semicrystalline.
  • Solvent resistance excellent; to evaluate this resistance, 7 test specimens according to French Standard NF T 51034 were immersed in the solvent, heated to a given temperature for a given time, and the mean radial tensile strength of the 7 test specimens was measured after this time. The solvent resistance was considered to be excellent when the tensile strength was reduced to a value which still represented at least 90% of the initial value.
  • Water uptake below 100 ppm; to measure this, the procedure was as given below: a test specimen according to French Standard NF T 51034 was dried at 150° C. for 3 hours, was weighed (w o ) and was then immersed in water at 23° C. for 48 hours; after this time period, the test specimen was removed from the water, its surface was wiped dry and it was reweighed (w): the water uptake is equal to w-w o /w o ⁇ 10 6 .
  • Test D and E show the criticality of the duration of the injection molding.
  • the injection molding time was 15 seconds and the warp angle was 0.9 ⁇ 10 -5 radian, while the surface roughness is greater than 1 ⁇ m.
  • the warp angle is as high as 3.5 ⁇ 10 -5 radian.
  • This example illustrates production of a magnetic disc according to the present invention, comprising a magnetic coating based on magnetic pigments.
  • the magnetic pigments represented 55% of the weight of the deposited and dry magnetic coating.
  • the coated substrate was treated to evaporate the solvent and was then subjected to a temperature of 190° C. for 4 hours to crosslink the binder resins.
  • the magnetic layer deposited had a thickness of 0.60 ⁇ m.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Magnetic Record Carriers (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
  • Polymers With Sulfur, Phosphorus Or Metals In The Main Chain (AREA)
  • Laminated Bodies (AREA)
  • Paints Or Removers (AREA)
  • Injection Moulding Of Plastics Or The Like (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
US07/418,964 1986-09-29 1989-10-10 Highly oriented thermotropic magnetic recording medium Expired - Fee Related US4987020A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8613714 1986-09-29
FR8613714A FR2604552A1 (fr) 1986-09-29 1986-09-29 Substrat polymere rigide utilisable comme support d'enregistrement magnetique et le disque magnetique obtenu a partir de ce substrat

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US07102479 Continuation-In-Part 1987-09-29

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US4987020A true US4987020A (en) 1991-01-22

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US (1) US4987020A (pt)
EP (1) EP0263043B1 (pt)
JP (1) JPS6391823A (pt)
KR (1) KR930004443B1 (pt)
CN (1) CN1012328B (pt)
AT (1) ATE57782T1 (pt)
BR (1) BR8704984A (pt)
DE (1) DE3765739D1 (pt)
DK (1) DK509787A (pt)
ES (1) ES2018293B3 (pt)
FR (1) FR2604552A1 (pt)
GR (1) GR3001262T3 (pt)
PT (1) PT85803B (pt)

Cited By (5)

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Publication number Priority date Publication date Assignee Title
US5707706A (en) * 1994-07-20 1998-01-13 Hitachi, Ltd. Magnetic recording disk medium having a magnetic layer with uniform properties over the disk surface
US20020155216A1 (en) * 2001-04-19 2002-10-24 Reitz John Bradford Spin coated media
US6715200B2 (en) 1999-02-12 2004-04-06 General Electric Company Methods for making data storage media
US7021363B2 (en) * 2000-04-27 2006-04-04 Sms Demag Mold wall, especially a broad side wall of a continuous casting mold for steel
US7179551B2 (en) 1999-02-12 2007-02-20 General Electric Company Poly(arylene ether) data storage media

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Publication number Priority date Publication date Assignee Title
CA2031216A1 (en) * 1989-03-31 1990-10-01 Takeshi Kamiya Molding method for magnetic disc substrate
JPH05320396A (ja) * 1991-01-31 1993-12-03 Unitika Ltd 軽量化ポリエステルフイルムおよびその製造方法
CN108085653A (zh) * 2017-12-20 2018-05-29 李春田 一种铝合金表面处理方法

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US4311824A (en) * 1978-10-05 1982-01-19 Rhone-Poulenc Industries Thermotropic alkylaromatic copolyesters
US4355133A (en) * 1981-07-27 1982-10-19 Celanese Corporation Polyester of 6-hydroxy-2-naphthoic acid, 4-hydroxy benzoic acid, 1,4-cyclohexanedicarboxylic acid, and aromatic diol capable of readily undergoing melt processing to form articles possessing high impact properties
US4652479A (en) * 1984-03-09 1987-03-24 Kabushiki Kaisha Toshiba Magnetic recording medium
US4680211A (en) * 1985-07-25 1987-07-14 The Dow Chemical Company Recording disks
US4719171A (en) * 1984-10-09 1988-01-12 Polyplastics Co., Inc. Optical disc

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US4248995A (en) * 1978-10-05 1981-02-03 Rhone-Poulenc Industries Process for the production of alkylaromatic copolyesters
US4311824A (en) * 1978-10-05 1982-01-19 Rhone-Poulenc Industries Thermotropic alkylaromatic copolyesters
US4284757A (en) * 1979-03-02 1981-08-18 Rhone Poulenc Industries Thermotropic aromatic copolyesters and processes for their preparation
US4355133A (en) * 1981-07-27 1982-10-19 Celanese Corporation Polyester of 6-hydroxy-2-naphthoic acid, 4-hydroxy benzoic acid, 1,4-cyclohexanedicarboxylic acid, and aromatic diol capable of readily undergoing melt processing to form articles possessing high impact properties
US4652479A (en) * 1984-03-09 1987-03-24 Kabushiki Kaisha Toshiba Magnetic recording medium
US4719171A (en) * 1984-10-09 1988-01-12 Polyplastics Co., Inc. Optical disc
US4680211A (en) * 1985-07-25 1987-07-14 The Dow Chemical Company Recording disks

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5707706A (en) * 1994-07-20 1998-01-13 Hitachi, Ltd. Magnetic recording disk medium having a magnetic layer with uniform properties over the disk surface
US5976661A (en) * 1994-07-20 1999-11-02 Hitachi, Ltd. Magnetic recording medium and method of fabricating the same
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US6715200B2 (en) 1999-02-12 2004-04-06 General Electric Company Methods for making data storage media
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KR880004440A (ko) 1988-06-07
EP0263043B1 (fr) 1990-10-24
ES2018293B3 (es) 1991-04-01
ATE57782T1 (de) 1990-11-15
FR2604552A1 (fr) 1988-04-01
CN1012328B (zh) 1991-04-10
DE3765739D1 (de) 1990-11-29
KR930004443B1 (ko) 1993-05-27
PT85803A (fr) 1987-10-01
GR3001262T3 (en) 1992-08-25
PT85803B (pt) 1990-08-31
DK509787D0 (da) 1987-09-28
BR8704984A (pt) 1988-05-17
DK509787A (da) 1988-03-30
CN87106605A (zh) 1988-04-06
EP0263043A1 (fr) 1988-04-06
JPS6391823A (ja) 1988-04-22

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